Pteronura

While Sea otters can also weigh up to 100 pounds, Giant otters are definitely the longest members of the weasel family, reaching five-and-a-half feet in length. Found in noisy groups of up to eight, related animals along rivers in tropical South America, they are active only during the day time. Although they have the shortest fur of any otter, their hides have been traditionally valued, and the fur trade has led to their being listed as an endangered species. Until recently, it was a very rare animal in zoos, but increasing numbers are being bred in captivity.